  static const GLenum conv_internal_format_table[] = {
    GL_ALPHA,
    GL_ALPHA4,
    GL_ALPHA8,
    GL_ALPHA12,
    GL_ALPHA16,
    GL_COMPRESSED_ALPHA,
    GL_COMPRESSED_LUMINANCE,
    GL_COMPRESSED_LUMINANCE_ALPHA,
    GL_COMPRESSED_INTENSITY,
    GL_COMPRESSED_RGB,
    GL_COMPRESSED_RGBA,
    GL_DEPTH_COMPONENT,
    GL_DEPTH_COMPONENT16,
    GL_DEPTH_COMPONENT24,
    GL_DEPTH_COMPONENT32,
    GL_LUMINANCE,
    GL_LUMINANCE4,
    GL_LUMINANCE8,
    GL_LUMINANCE12,
    GL_LUMINANCE16,
    GL_LUMINANCE_ALPHA,
    GL_LUMINANCE4_ALPHA4,
    GL_LUMINANCE6_ALPHA2,
    GL_LUMINANCE8_ALPHA8,
    GL_LUMINANCE12_ALPHA4,
    GL_LUMINANCE12_ALPHA12,
    GL_LUMINANCE16_ALPHA16,
    GL_INTENSITY,
    GL_INTENSITY4,
    GL_INTENSITY8,
    GL_INTENSITY12,
    GL_INTENSITY16,
    GL_R3_G3_B2,
    GL_RGB,
    GL_RGB4,
    GL_RGB5,
    GL_RGB8,
    GL_RGB10,
    GL_RGB12,
    GL_RGB16,
    GL_RGBA,
    GL_RGBA2,
    GL_RGBA4,
    GL_RGB5_A1,
    GL_RGBA8,
    GL_RGB10_A2,
    GL_RGBA12,
    GL_RGBA16,
    GL_SLUMINANCE,
    GL_SLUMINANCE8,
    GL_SLUMINANCE_ALPHA,
    GL_SLUMINANCE8_ALPHA8,
    GL_SRGB,
    GL_SRGB8,
    GL_SRGB_ALPHA,
    GL_SRGB8_ALPHA8,
  };
  internal_format = conv_internal_format_table[Int_val(_internal_format)];
#if defined(USE_MY_GL3_CORE_PROFILE)
  if (internal_format == 0x000A)
    caml_failwith("using gl-enum deprecated in core OpenGL 3");
#endif
